Trigun from Dirge of Cerberus

[Monkey D. Luffy]

But it wouldn't be any stronger than a punch?

The power will depend on your ATK, though with caveats that power can be embellished. For example, Luffy's Gomu Gomu Rifle is stronger than his Gomu Gomu Pistol, but requires longer prep time. Also since we allow players to add "charging" to their moves, that inherently makes them stronger.

Additionally, instead of separating the moves, you can add barrel types as variations to all three guns, giving them a cost of 600 (or 900 if all 3 guns can use all 3 barrel attachments).